蒸发式冷凝器国内外研究进展

介绍蒸发式冷凝器的工作原理、分类、特点及研究进展。具体阐述蒸发式冷凝器结构的改进,包括目前应用较为广泛的填料蒸发式冷凝器、鼓泡蒸发式冷凝器、板式蒸发式冷凝器等;传热研究方面分析了弹性管和扭曲管的优越性以及一些计算模型和设计程序;最后总结水处理及除垢技术的进展,并对今后的研究方向进行展望。     

蒸发式冷凝器的冬季运行

一、前言近几年来,青啤、燕京、华润、珠啤等各大型啤酒集团纷纷收购兼并扩产,各项技改工程纷纷启动,啤酒销量持续上扬,人们对啤酒的需求全年不断。与生产相关的制冷系统是常年运行。在我国北方,冬季气温常常降到0℃以下,所以制冷系统的蒸发式冷凝器在冬季运行时必须考虑循环水的防冻问题。     

关于蒸发式冷凝器布置的建议

近几年来，啤酒的需求量逐年增加，新建扩建的啤酒项目和麦牙项目纷纷上马，相关的制冷工艺流程的确定和设备的选用都吸收了国外的一些先进技术。蒸发式冷凝器具有冷凝效率高、占地面积小、节能等特点而被经常采用。由于蒸发式冷凝器必须保证充足的新鲜空气才能达到设计的冷凝排热量，故蒸发式冷凝器的布置对制冷系统的正常运行影响很大。本文以CXV型蒸发式冷凝器为例对蒸发式冷凝器的布置提供几点建议。     

蒸发式冷凝器替代立式冷凝器

蒸发式冷凝器作为制冷系统的主要热交换设备，由于采用了热力学、传热学等先进技术，单位面积的换热量大幅度提高，具有高效节能的优点。     

蒸发式冷凝器在啤酒生产中的应用

珠江啤酒股份有限公司一期冷冻站的氨冷却系统原使用卧式冷凝器，将高温高压的氨气冷凝成液氨。为减少环境污染和安全事故，2006年对制冷压缩机排气的冷却系统进行了改造。     

关于蒸发式冷凝器系统螺杆压缩机油冷却器冷源的建议

一、前言随着人们生活水平的提高,啤酒的需求量也在逐年增加,而啤酒质量的高低在很大程度上取决于糖化工段和发酵中制冷效果的好坏。近几年来,国内新建和扩建的啤酒项目,均在上规模、上档次,因此在制冷工艺流程的确定和设备的选用上,都吸收了国外的一些先进技术。尤其是蒸发式冷凝器,由于它的冷凝效率高,占地面积小,能耗少,以及配管简单尤其是节省了庞大的冷却水系统等特点,越来越受到啤酒厂家的青睐。但由此也带来了制冷系统管路设计上的一些新变化,尤其是如何解决螺杆压缩机由冷却器冷源的问题,     

改变蒸发冷凝器形式——节能降耗

在现代蒸发器的附属设备中，冷凝器是必不可少的，它的作用是将蒸发系统中产生的大量汁汽及时冷凝成为冷凝水，从而用真空泵将系统中的不凝性气体抽走，维持系统中的压力(真空)。冷凝器换热效率的高低，决定着蒸发器是否能够正常运行、冷凝器效率低，蒸发系统最终产生的大量汁汽就不能完全冷凝成为冷凝水，造成蒸发系统中的压力、温度升高，蒸发效率就会降低，产品质量也会因此降低，真空泵将不凝性气体和残存的汁汽抽走，也增加了真空泵的负荷。     

甜菜糖厂蒸发系统设计计算

作者根据工程设计实践,对甜菜糖厂蒸发系统的设计计算结呆进行了总结,该方案立足于系统的先进性、稳定性和灵活性,对同行有一定的借鉴意义。     

园筒水帘式混合冷凝器的设计

去年5月份我们公司增添了一台25.6m3／20m3(全容积／使用容积)的强制循环结晶锅。与之配套，本人设计了一台园筒水帘式混合冷凝器，使用效果较好。兹介绍如下，以供经验交流。……     

葡萄糖生产蒸发过程的节能及设计计算的探讨

<正> 在葡萄糖生产过程中,蒸发过程需要消耗大量的能量。因此,采用合理的蒸发工艺流程与切实可行的节能措施,对于降低生产成本,提高经济效益有着重大的意义。 目前葡萄糖生产过程中蒸发工艺流程和设备的概况及其分析     

蒸发冷却＋辐射供冷空调系统的设计

根据蒸发冷却和辐射供冷的热湿处理空调特性,利用焓湿图分配其热湿负荷．计算辐射供冷水侧的供回水温度、流量、供冷能力等．给出了蒸发冷却新风的送风状态点和送风量的求解结果,并给出了冷源设备的选型方法．     

CFD预测不同进风方向对蒸发式冷凝器流场的影响

为能够准确真实地研究蒸发式冷凝器工作状态下内部温度场和气流场的变化情况,建立蒸发式冷凝器三维模型,利用CFD模拟软件Fluent对蒸发式冷凝器工作状态时内部流场进行非稳态模拟,并分析5s内3种进风方向(壳体单面进风、壳体双面进风、壳体双面顶部一面进风)对冷凝器内部温度场以及气流场的影响。结果表明:单面进风时,冷气流水平侵入冷凝器底部,在密度差作用下上升并与冷凝盘管进行换热;双面进风与单面进风相比,能够减少管壁和壁面处漩涡的数量与强度;三面进风时,冷凝器内腔温度经历一个短暂下降再上升的过程。在今后的设计中,还可以通过改变进风面积以及进风角度等参数来优化蒸发式冷凝器的换热效率。     

一种板式间接蒸发冷却器数学模型的验证

对J．Stoitchkov建立的关于叉流板式间接蒸发冷却器的数字模型进行了理论计算及实验验证，结果表明，理论值与实验值的相对误差不大于10％．用该模型计算了一次风量、二次风量、淋水量及隔板厚度对一次风出口温度的影响．     

衣下间隙对织物系统热湿阻的影响

为研究人体皮肤与织物之间存在的衣下间隙对织物系统传热透湿性能的影响,利用出汗热平板仪测试织物系统的热阻和湿阻,并通过在热板与织物之间放置不同厚度的分隔板来模拟衣下间隙厚度,实现了定量测试皮肤—衣下间隙—织物之间的热湿传递。实验结果证明:织物系统的热阻和湿阻先随衣下间隙厚度的增大而增加,但在衣下间隙达到12 mm时出现下降,随后又进一步增加;虽然织物厚度影响着织物系统的热阻与湿阻,但衣下间隙对织物系统热湿阻的影响更为显著。综合服装的合体美观与舒适保暖性能,建议防寒类服装设计采用胸围放松量6~8 cm之间为宜。本研究有助于理解服装宽松量设计与服装隔热透湿性能之间的相互关系,对服装产品的舒适设计有指导意义。     

Study on thermal and evaporative resistances of multilayered fabric ensembles

The present work deals with the study on thermal and evaporative resistance of multilayered fabric ensembles meant for cold weather applications. Three-layered structure is used to study the thermal comfort properties. Knitted fabric and polytetrafluoroethylene coated fabrics were used in inner and outer layer, respectively. Needle punched fabrics produced from polyester fibre were used in middle layer. Fifteen different non-woven fabrics were produced according to Box and Behnken experimental design for three variables and three levels by varying mass per unit area, punch density and depth of needle penetration. The produced fabrics were evaluated for thermal and evaporative resistances with and without inner and outer layer fabrics. Thickness, air permeability, bulk density and porosity of the needle punched fabrics were studied. The properties of the fabrics were analyzed for statistical significance by using ‘Design-Expert’ statistical software. Artificial neural network model was developed to predict the properties of fabrics and validation of model was done with the testing data-set. The performance of prediction was evaluated by mean square error, mean absolute error percentage and correlation coefficient. It was concluded that the predicted properties of fabric correlated well with the experimental results.     

蒸发光散射检测器的清洗方法

目的建立一种蒸发光散射检测器的清洗方法。方法在高温氮气流的作用下,利用高浓度的盐酸溶液去除蒸发光散射检测器蒸发管内壁的奶垢;依次用丙酮、乙腈、甲醇、水溶液清洗之后,高温氮气流的作用下继续烘烤;清洗结束后,对蒸发光散射检测器进行面积归一化。结果乳糖在0～4mg/mL范围内,浓度与峰面积采用幂函数方程绘制标准曲线,相关系数大于0.99,检出限为190 mg/100 g;样品的加标平均回收率为96.45%～103.16%,相对标准偏差为3.88%～5.18%;对清洗前后的蒸发光散射检测器进行10次重复性测试,相对标准偏差为0.66%,清洗后检测信号增大2倍,仪器噪音减少4倍。结论本方法适用于蒸发光散射检测器的彻底清洗,可以减少更换蒸发管的次数。     

Extending the potential of evaporative cooling for heat-stress relief

Factors were analyzed that limit the range of environmental conditions in which stress from heat may be relieved by evaporative cooling in shaded animals. Evaporative cooling reduces air temperature (Ta), but increases humidity. Equations were developed to predict Ta reduction as a function of ambient temperature and humidity and of humidity in cooled air. Predictions indicated that a reduction of Ta becomes marginal at humidities beyond 45%. A reduction of Ta lessens with rising ambient Ta. The impact of increasing humidity on respiratory heat loss (Hre) was estimated from existing data published on Holstein cattle. Respiratory heat loss is reduced by increased humidity up to 45%, but is not affected by higher humidity. Skin evaporative and sensible heat losses are determined not only by the humidity and temperature gradient, but also by air velocity close to the body surface. At higher Ta, the reduction in sensible heat loss is compensated for by an increased demand for Hre. High Hre may become a stressor when panting interferes with resting and rumination. Effects of temperature, humidity, air velocity, and body surface exposure to free air on Hre were estimated by a thermal balance model for lactating Holstein cows yielding 35 kg/d. The predictions of the simulations were supported by respiratory rate observations. The Hre was assumed to act as a stressor when exceeding 50% of the maximal capacity. When the full body surface was exposed to a 1.5 m/s air velocity, humidity (15 to 75%) had no significant predicted effect on Hre. For an air velocity of 0.3 m/s, Hre at 50% of the maximum rate was predicted at 34, 32.5, and 31.5° C for relative humidities of 55, 65, and 75%, respectively. Similar results were predicted for an animal with two-thirds of its body surface exposed to 1.5 m/s air velocity. If air velocity was reduced for such animals to 0.3 m/s, the rise in Hre was expected to occur at approximately 25° C and 50% relative humidity. Maximal rates of Hre were estimated at 27 to 30° C when ambient humidity was 55% relative humidity and higher. High humidity may stress animals in evaporative cooling systems. Humidity stress may be prevented by a higher air velocity on the body surface of the animal, particularly in sheltered areas in which the exposed body surface is reduced, such as mangers and stalls. This may extend the use of evaporative cooling to less dry environments.     

蒸发型降温服的降温性能研究

为缓解高温环境下作业人员的热应激,利用高分子蓄冷材料设计降温服。通过模拟热环境(34℃),利用恒功率控制干态暖体假人,选择3个劳动强度水平(即20、200和300 W/m²)和3个相对湿度水平(即20%、50%和80%)对该降温服的降温性能进行系统的研究。结果表明：该降温服能降低假人的皮肤温度,各部位皮肤温度最大降温梯度为3.4℃,最大初期降温速度为0.081℃/min;劳动强度对降温服的有效降温时长存在显著影响,在所选劳动强度下的躯干有效降温时长分别为大于420、165和102 min;相对湿度对降温服的降温梯度存在显著影响,在所选相对湿度水平下的躯干降温梯度分别为1.8、1.2和0.4℃。该蒸发型降温服降温过程缓和,无骤冷、过冷现象,适合中等劳动强度、中等相对湿度环境下穿着。     

Statistical and ANN analysis of thermal and evaporative resistances of multilayered fabric ensembles

In this paper, thermal and evaporative resistance of multilayered fabrics meant for cold weather conditions have been reported. Polyester hollow fibers of 6 denier and 15 denier were used to produce needle-punched fabrics. Full factorial experimental design was used to produce 30 different needle-punched nonwoven fabrics from two different linear densities of fiber by varying mass per unit area and punch density at three and five different levels, respectively. The needle-punched nonwovens were used as insulative middle layer. Single jersey knitted fabric and polytetrafluoroethylene-coated fabric was used as inner and outer layer, respectively. The multilayered fabric ensembles were evaluated for thermal and evaporative resistance using sweating guarded hot plate (SGHP) system. Regression equations were developed to draw the contour plots and to analyze the effect of different parameters on thermal and evaporative resistance of fabrics. Two independent one-way analysis of variance (ANOVA) were conducted to find the significance of linear density of fiber and effect of inner and outer layers on thermal and evaporative resistance of fabrics. The two-way ANOVA was conducted to analyze the effect of mass per unit area and punch density on thermal properties of fabrics and ‘F’ values were calculated. Mean square values of pure error and lack of fit were studied to analyze the fitness of the developed model for thermal properties of fabrics. An artificial neural network (ANN) model was developed to predict the thermal and evaporative resistance of multilayered fabrics and compared with the experimental values. It has been observed that the ANN model predicts the thermal and evaporative resistance of multilayered fabrics with high degree of accuracy.